Take CoolEdit Pro v1.2, create a WAVE there - 24 bit, 96 kHz. It is real 24 bit 96 kHz, not a fake - it works with
Terratec fine, as well as with more professional hardware.
Create a sine-wave (Generate -> Tones) with frequency raising from 20 Hz to 48 kHz.
Now, start another CoolEdit Pro session, create an empty WAVE with the same parameters - 24 bit, 96 kHz. Set your Surround Mixer to record from WAVE output. It is digital, right? No conversions should be performed - signal shouldn't even leave digital circuits.
Now put the first CoolEdit Pro to playback and the second one - to record. If Audigy was true 24 bit 96 kHz, you'd get about the same type of wave in the second one - sine from 20 Hz to 48 kHz. But you won't. All you'll get is 24 kHz maximum, which is 48 kHz sampling rate.